Product Code: ICAL07_1609

Zinc Sulfide Optics for High Power Laser Applications
Authors:
Stanley Ream, EWI; Columbus OH USA
Wei Zhang, EWI; Columbus OH USA
Craig Walters, CWA; Dublin OH USA
Greg Firestone, EWI; Columbus OH USA
Presented at ICALEO 2007

As higher power disc and fiber lasers become available, questions arise concerning the stability and durability of focusing optics. Even at familiar YAG power and brightness (i.e. 4 kW from 600 um fiber) focusing optics are known to exhibit shifts in position and changes in focal spot size. At higher power levels these focusing issues will become significantly more troublesome. Traditional 1.06/1.07 um focusing optics are constructed from multiple, fused silica, optical elements. An entire focusing assembly (with camera viewing) may include 5 quartz optics, each one of which can contribute to thermally-induced focal spot shift or distortion. Newly available, diamond machinable, multi-spectral zinc sulfide, optical material offers potential benefits for stable focusing of high power beams. While the absorption characteristics of this material are higher than those for fused silica, it has about 25 times the thermal conductivity, which permits much more efficient heat removal and improved thermal stability. Additionally, the ability of this material to be diamond machined permits a reduction in the number of optical elements required to achieve optimum focal spot quality. This paper will provide thermal modeling results and focal stability test results of an experimental ZnS lens, coupled to a 10 kW fiber laser.